How C # recognizes if a string is in JSON format

How C # identifies whether a string is in JSON format:

Using system;using system.collections.generic;using system.text;namespace cyq.    data.tool{//<summary>///delimited JSON string as a dictionary collection.            </summary> Internal class Jsonsplit {private static bool Isjsonstart (ref string JSON) { if (!string. IsNullOrEmpty (JSON)) {JSON = json.                Trim (' \ r ', ' \ n ', '); if (JSON.                    Length > 1) {char s = json[0]; Char e = Json[json.                    LENGTH-1]; return (s = = ' {' && e = = '} ') | |                (s = = ' [' && e = = '] ');        }} return false;            } internal static bool Isjson (string json) {int errindex;        Return Isjson (JSON, out errindex);            } internal static bool Isjson (string json, out int errindex) {errindex = 0;  if (Isjsonstart (ref JSON)) {Charstate cs = new Charstate ();              char c; for (int i = 0; i < JSON. Length;                    i++) {c = json[i];                    if (Setcharstate (c, ref CS) && Cs.childrenstart)//Set key symbol status. {String item = JSON.                        Substring (i);                        int err;                        int length = Getvaluelength (item, True, out err);                        Cs.childrenstart = false;                            if (Err > 0) {errindex = i + err;                        return false;                    } i = i + length-1;                        } if (cs.iserror) {errindex = i;                    return false;            }} return!cs.arraystart &&!cs.jsonstart;        } return false;   }//<summary>     Gets the length of the value (when the JSON value is nested at the beginning of "{" or "[")///</summary> private static int getvaluelength (string json, Boo            L BREAKONERR, out int errindex) {errindex = 0;            int len = 0; if (!string.                IsNullOrEmpty (JSON)) {Charstate cs = new Charstate ();                char c; for (int i = 0; i < JSON. Length;                    i++) {c = json[i]; if (!                    Setcharstate (c, ref CS))//Set key symbol status.                        {if (!cs.jsonstart &&!cs.arraystart)//json end, not an array, exits.                        {break;                    }} else if (Cs.childrenstart)//normal character, value state. {int length = Getvaluelength (JSON.                        Substring (i), Breakonerr, out errindex);//recursive sub-value, return a length ...                        Cs.childrenstart = false; Cs.valuestart = 0;                       cs.state = 0;                    i = i + length-1;                        } if (Breakonerr && cs.iserror) {errindex = i;                    return i;                    } if (!cs.jsonstart &&!cs.arraystart)//record the current end position.                    {len = i + 1;//length peso citation +1 break;        }}} return len;            }///<summary>///character status//</summary> private class Charstate {            internal bool Jsonstart = false;//begins with "{" ... internal bool Setdicvalue = false;//You can set the dictionary value. internal bool Escapechar = false;//begins with the "\" escape sign///<summary>/////array start "Only First", Value nested with "childrens            Tart "to identify. </summary> internal bool Arraystart = false;//begins with the "[" Symbol Internal bool Childrenstart = false;//Child nesting begins. <summary>//"0 initial state, or encountered", "comma"; "1 encountered": "Colon"///</summary> Internal int            state = 0;            <summary>//"1 Value End" "0 Not Started" "1 no quotation marks start" "2 single quote Start" "3 double quotation mark start"//</summary>            internal int keystart = 0;            <summary>//"1 Value End" "0 Not Started" "1 no quotation marks start" "2 single quote Start" "3 double quotation mark start"//</summary>            internal int valuestart = 0;            internal bool IsError = false;//is a syntax error. internal void Checkiserror (char c)//is only processed as a first level (because the getlength is recursive to each child processing) {if (Keystart > 1 | | val                Uestart > 1) {return; }//Example ["AA", {"BBBB": 123, "FFF", "ddd"}] switch (c) {case ' {'://[{' [{A}] ": [{" [{B}] "": 3, "M": "C"}]}] IsError = Jsonstart && state = = 0;//repeat startErrors are not value-handling at the same time.                    Break Case '} ': IsError =!jsonstart | | (Keystart! = 0 && state = = 0);//repeat end error or end prematurely {"AA"}.                    The normal has {} break;                    Case ' [': IsError = arraystart && state = = 0;//repeat start error break; Case '] ': isError =!arraystart | |                    jsonstart;//Duplicate start error or Json does not end break; Case ' ': Case ' \ ': IsError =! (Jsonstart | | arraystart);                        The JSON or array begins.  if (!iserror) {//repeat start ["", {"" "}] IsError = (state = = 0 && Keystart = =-1) | |                        (state = = 1 && Valuestart = =-1);           } if (!iserror && arraystart &&!jsonstart && c = = ' \ ')//[' AA ', {}]             {IsError = true;                    } break; Case ': ': isError =!jsonstart | |                        The state = = 1;//repeats itself.                    Break Case ', ': IsError =! (Jsonstart | | arraystart);                        The JSON or array begins.                                if (!iserror) {if (Jsonstart) { IsError = state = = 0 | |                            (state = = 1 && valuestart > 1);//repeated appearance.                                } else if (arraystart)//["AA," [,] [{},{}] {                            IsError = Keystart = = 0 &&!setdicvalue;                    }} break; Case ': Case ' \ r ': Case ' \ n '://["a", \r\n{}] Case' + ': case ' \ t ': break;                        Default://value begins with. IsError = (!jsonstart &&!arraystart) | | (state = = 0 && Keystart = =-1) | |                (Valuestart = =-1 && state = = 1);//break;        }//if (IsError)//{//}}}//<summary> Sets the character state (returns true as the keyword, returns false when the normal character is processed)///</summary> private static bool Setcharstate (char C, r EF Charstate CS) {cs.            Checkiserror (c);                    Switch (c) {case ' {'://[{"[{A}]": [{"[{B}]": 3, "M": "C"}]}] #region curly braces if (cs.keystart <= 0 && cs.valuestart <= 0) {Cs.keys                        Tart = 0;                        Cs.valuestart = 0;                      if (cs.jsonstart && cs.state = = 1)  {Cs.childrenstart = true;                        } else {cs.state = 0;                        } Cs.jsonstart = true;//started.                    return true;                } #endregion break; Case '} ': #region curly braces End if (cs.keystart <= 0 && Cs.valuestart < 2 &amp                        ;& cs.jsonstart) {Cs.jsonstart = false;//ends normally.                        cs.state = 0;                        Cs.keystart = 0;                        Cs.valuestart = 0;                        Cs.setdicvalue = true;                    return true;                    }//Cs.iserror =!cs.jsonstart && cs.state = = 0;                #endregion break; Case ' [': #region EnclosedNumber starts if (!cs.jsonstart) {Cs.arraystart = true;                    return true; } else if (cs.jsonstart && cs.state = = 1) {Cs.childr                        Enstart = true;                    return true;                } #endregion break; Case ': #region brackets End If (cs.arraystart &&!cs.jsonstart && Cs.key                    Start <= 2 && cs.valuestart <= 0)//[{},333]//this end.                        {Cs.keystart = 0;                        Cs.valuestart = 0;                        Cs.arraystart = false;                    return true;                } #endregion break; Case ' ': Case ' \ ': #region quotation marks if (Cs.jsonstart | | Cs. Arraystart) {if (cs.state = = 0)//key stage, possibly array ["AA", {}] {if (cs.keystart <= 0) {Cs.keyst Art = (c = = ' "'?                                3:2);                            return true; } else if ((Cs.keystart = = 2 && c = = ' \ ') | |                            (Cs.keystart = = 3 && c = = ' ")) {if (!cs.escapechar) {C                                    S.keystart =-1;                                return true; } else {Cs.escapechar =                                False }}} else if (cs.state = = 1 && cs.jsonst ART)//value stage must beIt's JSON started. {if (cs.valuestart <= 0) {Cs.val Uestart = (c = = ' "'?                                3:2);                            return true; } else if ((Cs.valuestart = = 2 && c = = ' \ ') | |                            (Cs.valuestart = = 3 && c = = ' ")) {if (!cs.escapechar) {C                                    S.valuestart =-1;                                return true; } else {Cs.escapechar =                                False                    }}} #endregion                Break Case ': ': #region Colon if (cS.jsonstart && Cs.keystart < 2 && Cs.valuestart < 2 && cs.state = = 0) {                        if (Cs.keystart = = 1) {Cs.keystart =-1;                        } cs.state = 1;                    return true; }//Cs.iserror =!cs.jsonstart | |                    (Cs.keystart < 2 && Cs.valuestart < 2 && cs.state = 1);                #endregion break;                        Case ', ': #region comma//["AA", {aa:12,}] if (Cs.jsonstart) {                             if (Cs.keystart < 2 && Cs.valuestart < 2 && cs.state = 1) {                            cs.state = 0;                            Cs.keystart = 0;                            Cs.valuestart = 0;               if (Cs.valuestart = = 1)             {//Cs.valuestart = 0;                            } Cs.setdicvalue = true;                        return true;                        }} else if (Cs.arraystart && cs.keystart <= 2) {                        Cs.keystart = 0;                        if (Cs.keystart = = 1)//{//Cs.keystart =-1;                    } return true;                } #endregion break; Case ': Case ' \ r ': Case ' \ n '://["a", \r\n{}] case ' + ': CAs                    E ' \ t ': if (cs.keystart <= 0 && cs.valuestart <= 0)//cs.jsonstart &&                    {return true;//skips a space.          } break;      Default://value begins with.                            if (c = = ' \ \ ')//Escape symbol {if (Cs.escapechar) {                        Cs.escapechar = false;                            } else {Cs.escapechar = true;                        return true;                    }} else {Cs.escapechar = false;                    } if (Cs.jsonstart | | cs.arraystart)//Json or array begins.                            {if (cs.keystart <= 0 && cs.state = = 0) { Cs.keystart = 1;//without quotation marks} else if (cs.valuestart <= 0 && CS.S                        Tate = = 1 && cs.jsonstart)//Only JSON starts with a value.               {cs.valuestart = 1;//without quotation marks         }} break;        } return false; }    }}

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